For the first two, based on personal experience:
Anecdotally, my old back-mounted LG fingerprint scanner has never been wrong (when dry of course), but my Pixel needs a re-scan 30% of the time.
My phone requires a tap to wake the screen before the fingerprint reader will accept any input at all, unless I decide to burn battery and turn on AOD.
E: My current phone uses an optical sensor and, from what I understand, ultrasonics are infinitely better
Hm… It’s out of date for sure, but I just tried it and it definitely works for both Lemmy and Reddit. You can add any instance you’d like to a custom feed.